package com.hmdp.service.impl;

import ch.qos.logback.core.net.server.Client;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.apache.ibatis.annotations.Results;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    @Override
    public Result queryById(Long id) {
        // 缓存穿透
        // Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        // 互斥锁解决缓存击穿
        // Shop shop = queryWithLogicalExpire(id);

        // 逻辑过期解决缓存击穿
        Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, 20L, TimeUnit.MINUTES);
        if (shop==null) {
            return Result.fail("店铺不存在");
        }
        //返回
        return Result.ok(shop);
    }

    public Shop queryWithMutex(Long id){
        String key = CACHE_SHOP_KEY + id;
        // 1 从redis里查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        // 2 判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            // 3 存在, 直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        // 判断命中的是不是空值
        if(shopJson != null){
            // 返回一个错误信息
            return null;
        }
        // 4. 实现缓存重建
        // 4.1 获取互斥锁
        Shop shop = null;
        try {
            boolean isLock = tryLock(LOCK_SHOP_KEY);
            // 4.2 判断是否获取成功
            if (!isLock){
                // 4.3 失败,则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            // 4.4 获取🔒成功, 根据Id查询数据库
            shop = getById(id);
            // 模拟重建延迟
            Thread.sleep(200);
            // 5 不存在, 返回错误, 将空值写入Redis
            if(shop == null){
                // 空值写入Redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            // 6 存在, 写入Redis然后返回
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            // 7. 释放互斥锁
            unlock(LOCK_SHOP_KEY);
        }
        return shop;
    }

    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        // 1 从redis里查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2 判断是否存在
        if (StrUtil.isBlank(shopJson)){
            // 3 不存在, 直接返回
            return null;
        }

        // 4 命中, 需要把Json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject)redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5. 判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            // 5.1 未过期,直接返回店铺信息
            return shop;
        }
        // 5.1 已经过期, 需要缓存重建
        // 6 缓存重建
        // 6.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        // 6.2 判断是否获取锁成功
        if (isLock){
            // TODO 6.3 成功, 开启线程执行缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    // 重建缓存
                    saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    // 释放锁
                    unlock(lockKey);
                }
            });
        }

        // 6.4 失败, 返回过期商品信息
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        return shop;
    }

    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY + id;
        // 1 从redis里查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        // 2 判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            // 3 存在, 直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        // 判断命中的是不是空值
        if(shopJson != null){
            // 返回一个错误信息
            return null;
        }
        // 4 不存在, 根据Id查询数据库
        Shop shop = getById(id);
        // 5 不存在, 返回错误, 将空值写入Redis
        if(shop == null){
            // 空值写入Redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        // 6 存在, 写入Redis然后返回
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        return shop;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null){
            return Result.fail("店铺ID不能为空");
        }
        // 更新数据库
        updateById(shop);
        // 删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }

    public void saveShop2Redis(Long id, Long expireSeconds) throws InterruptedException {
        // 查询店铺信息
        Shop shop = getById(id);
        Thread.sleep(200);
        // 封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY+id, JSONUtil.toJsonStr(redisData));
        // 写入redis
    }
}
